Variety of nonlinear wave-breaking

We discuss the formation of typical (structurally stable) singularities in nonlinear wave breaking in stable and unstable media. The wake wave-break due to the inhomogeneity of the Langmuir frequency is accompanied by electron injection into the acceleration phase. In a wake wave excited behind a finite width laser pulse, the wave-breaking mechanism involves the increase, with the distance behind the pulse, of the curvature of the wake front, followed by the self-intersection of the electron trajectories. In the long wavelength limit, the Weibel instability which leads to the generation of a strong magnetic field, the relativistic self focusing and the Rayleigh-Taylor instability of a thin plasma slab provide examples of a common behavior with the rarefaction wave-breaking in unstable media. We present a solution of the Cauchy problem that describes the evolution of nonlinear perturbations of the Rayleigh-Taylor instability in terms of analytical functions of a complex variable.     

Preparation of Al-doped ZnO transparent electrodes suitable for thin-film solar cell applications by various types of magnetron sputtering depositions

In order to determine the influence of different types of magnetron sputtering (MS) depositions on the characteristics of Al-doped ZnO (AZO) thin films appropriate for applications as transparent electrodes in thin-film solar cells, transparent conducting AZO thin films were prepared on glass substrates at 200 °C by direct current (dc) magnetron sputtering (dc-MS), radio frequency (rf)-MS and rf power superimposed dc-MS (rf + dc-MS) depositions using an MS apparatus with the same AZO target. AZO thin films prepared by an rf + dc-MS deposition exhibited both a higher deposition rate than that found with rf-MS depositions and a lower resistivity or higher Hall mobility than those found with dc-MS. The lower dc sputter voltage featured in rf-MS and rf ± dc-MS depositions, producing smoother surface morphology and better crystallinity than obtained with dc-MS depositions. The light scattering characteristics of surface-textured AZO thin films prepared by various types of MS depositions were evaluated by observing the surface texture and measuring the optical transmittance and the diffusive component; wet-chemical etching of the thin film surface was performed in a 0.1% HCl solution. The obtainable haze property in the range from visible to near infrared in AZO films prepared by an rf + dc-MS deposition was markedly better than that obtained with dc-MS depositions.     

Prediction of mill load in hot strip mill rolling

It has been ascertained whether or not the model capable of predicting the stress-strain relation of plain carbon steels, previously proposed, is applicable to the estimation of mill loads in the finishing process (consisting of six mill stands) of a hot strip mill. An appreciably good agreement with the predicted and measured mill load values has been obtained in the earlier passes where the strip microstructure is regarded to have completed static recrystallization, and the predicted mill loads in the later passes have been far less than the measured load owing to the effect of the strain accumulated in the previous rolling process. Then, a simple model to predict the accumulated strain has been constructed and introduced into the calculation of mill loads. As a result, the predicted mill loads have been fairly improved over the whole passes in the finishing process.     

Highly dispersed Ni catalysts on carbon from thermal decomposition of cellulose-hydrous nickel gel membrane

Ultra fine particles were impregnated by using a finely porous cellulose gel membrane. The impregnated gel membrane is a green transparent one and looks like a solid solution. Highly dispersed Ni catalysts on carbon were obtained from thermal decomposition of these gel membranes. The particle size is in the range of several nm to a few ten nm. They show interesting catalytic properties for hydrogenation of olefins such as cyclooctadiene.     

Scalability of spectrum-sliced DWDM transmission and its expansion using forward error correction

This paper clarifies the scalability of spectrum-sliced dense wavelength-division-multiplexing (DWDM) transmission systems primarily intended for metro access applications. A theoretical analysis elucidates the tradeoff between the loss budget and the sliced bandwidth (i.e., the number of channels with assuming light sources with a fixed bandwidth). Moreover, the use of forward error correction (FEC) to expand scalability is studied. Based on the analysis, two spectrum-sliced DWDM transmission schemes are introduced. One demonstrates 1.25-Gb/s, eight channel spectrum-sliced DWDM transmission through the use of directly modulated super-luminescent diodes (SLDs), and the other confirms 10-Gb/s, eight channel spectrum-sliced DWDM transmission with the channel spacing of 200 GHz through the use of FEC.     

Local motion of crosslinks for poly (methyl methacrylate) gels by the fluorescence depolarization method

Poly(methyl methacrylate) (PMMA) gels labeled at crosslinks with anthracene were prepared. Anthracene fluorescence depolarization was monitored to probe the local motion of crosslinks for PMMA gels at different equilibrium swelling states. The relaxation times and the activation energies of local motion were measured for PMMA gels at the swollen states in various solvents through fluorescence anisotropy decays. The local motion of PMMA gel at crosslinks became faster with the increase of swelling ratio. When the swelling ratios were almost the same, the mobility of crosslinks was the same irrespective of the molecular weights between crosslinks. These results indicate that the local motion of crosslinks for PMMA gel is mainly governed by the segment density of network chains in the vicinity of crosslinks. Received: 31 March 1997/Revised: 11 April 1997/Accepted: 21 April 1997     

Stoichiometry of III–V compounds

Effects of stoichiometry control on electrical, optical and crystallographic features in III–V compounds are shown. The application of the optimum vapor pressure during annealing and crystal growth is shown to minimize the deviation from stoichiometric composition. Temperature-dependence of the optimum vapor pressure is also obtained. In view of the defect formation mechanism, existence of the stable interstitial arsenic atoms (I_As) in GaAs is emphasized. The mechanism of stoichiometry control is discussed on the basis of the equality of chemical potentials and the change of saturating solubility in the liquidus phase as a function of the vapor pressure.     

Geranial: the alarm pheromone in the nymphal stage of the oribatid mite,Nothrus palustris

The presence of an alarm pheromone was demonstrated in the deutonymphal stage of the oribatid mite, Nothrus palustris (C. L. Koch). The active principle was identified as 3,7-dimethyl-(E)-2,6-octadienal, geranial, and was shown to be active at doses of 10–100 ng. This is the first such pheromone identified in oribatid mites.